Gallium naphthalocyanine salts exhibiting reduced kogation

ABSTRACT

A sulfonated dye salt of formula (II): 
     
       
         
         
             
             
         
       
     
     wherein
     M is Ga(A 1 );   A 1  is an axial ligand selected from the group consisting of: —OH and halogen; and   Z 1   + , Z 2   + , Z 3   +  and Z 4   +  are independently selected from the group consisting of: H and an ammonium cation including 3 or more hydroxyl groups. At least one of Z 1   + , Z 2   + , Z 3   +  and Z 4   +  is the ammonium cation. Such salts exhibit reduced kogation in thermal bubble-forming inkjet printheads.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S.application Ser, No. 12/466,337 filed May 14, 2009, which is hereinincorporated by reference.

FIELD OF THE INVENTION

The present application relates to sulfonated dyes suitable for printinginks, such as inkjet inks. It has been developed primarily for reducingkogation of such dyes in an inkjet printhead.

CO-PENDING APPLICATIONS

The following applications have been filed by the Applicant:

Ser. Nos. 12/368,305 12/368,306

The disclosures of these co-pending applications are incorporated hereinby reference.

CROSS-REFERENCES TO RELATED APPLICATIONS

The following patents or patent applications filed by the applicant orassignee of the present invention are hereby incorporated bycross-reference.

10/815,635 7,357,323 7,605,940 7,506,168 7,905,401 7,457,961 7,457,0076,902,255 7,204,941 7,278,727 7,423,145 7,122,076 7,148,345 7,658,7927,837,775 7,416,280 6,755,509 7,156,289 7,721,948 6,720,985 7,295,8397,593,899 7,068,382 7,094,910 7,062,651 6,644,642 6,549,935 6,987,5736,727,996 6,760,119 7,064,851 6,290,349 6,428,155 6,785,016 6,831,6826,741,871 6,965,439 7,663,780 6,870,966 6,474,888 6,724,374 6,788,9827,263,270 6,788,293 6,737,591 7,369,265 10/778,056 11/193,482 7,055,7396,830,196 7,182,247 7,082,562 7,918,404 7,108,192 12/025,746 12/025,76212/025,765 10/492,169 7,469,062 7,359,551 7,444,021 7,308,148 6,957,7687,170,499 11/856,061 7,762,453 7,821,507 12/015,507

BACKGROUND OF THE INVENTION

Chemical dyes are important compounds for a range of applications. Forexample, inkjet inks typically comprise at least one colorant in theform of a dye. Many dyes are charged molecules carrying either apositive or negative charge, which is balanced with a counterion. Thepresent invention specifically relates to cationic salts of sulfonateddyes, such as sulfonated phthalocyanine dyes.

Sulfonated phthalocyanine dyes are useful in inkjet ink applications.For example, sulfonated copper phthalocyanines are well-known cyan dyes.More recently, the present Applicant has shown that sulfonated galliumnaphthlocyanines are useful IR dyes having minimal visibility andexcellent ozonefastness. Accordingly, sulfonated galliumnaphthlocyanines have found utility in the Applicant's Netpage andHyperlabel™ systems.

The Netpage and Hyperlabel™ systems generally require a substrate havinga position-coding pattern printed thereon. The coding pattern ispreferably printed with an IR-absorbing ink having minimal visibility,so that it does not interfere with the visible content of the substrate.A user can interact with the substrate using an optical sensing device,which reads part of the coding pattern and generates interaction data.This interaction data is transmitted to a computer system, which usesthe data to determine what action is being requested by the user. Forexample, a user may make handwritten input onto a form, click on aprinted hyperlink, or request information relating to a product item.This input is interpreted by the computer system with reference to apage description corresponding to the printed substrate.

Position-coding patterns for Netpage and Hyperlabel™ may be printed byanalogue (e.g. offset) or digital (e.g. inkjet) printers. If theposition-coding pattern is printed using an inkjet printer, it isimportant that the printhead has excellent longevity. Preferably, an IRchannel in the printhead, used for printing the coding pattern, shouldhave at least as good longevity as other color channels used forprinting graphics, text etc.

Kogation is a term used to describe a phenomenon whereby residues aredeposited over time on a heater element in an inkjet printhead. Kogationtypically occurs from repeated firing of a heater element and isgenerally understood to result from high-temperature deposition of inkcomponent residues. Usually, the inkjet dye (or pigment) is responsiblefor kogation on inkjet heater elements.

Therefore, an important characteristic of inkjet inks in thermal inkjetprinting is their propensity to kogate on a heater element. Ideally, aninkjet dye should exhibit minimal kogation, which consequently improvesthe lifetime of an inkjet printhead.

One approach to minimizing kogation is to add relatively large amountsof surfactant or other additives to the ink vehicle. For example, U.S.Pat. No. 6,533,851 describes phosphonate additives for inkjet inks,which are claimed to reduce kogation. However, additives of this typegenerally compromise print quality by increasing intercolor bleed.

Another approach to the problem of kogation is to simply ignore thekogate and ‘overpower’ the heater elements so that water is superheatedthrough the kogate. This approach is unsatisfactory in the Applicant'sMemjet® printheads, which use minimal ink ejection energy for eachnozzle so as to achieve high-speed pagewidth printing. Overpowering eachnozzle would inevitably compromise print speed and/or nozzle density.

It would therefore be desirable to provide an inkjet dye, which exhibitsreduced kogation. It would be further desirable to provide anIR-absorbing inkjet dye, which exhibits reduced kogation.

SUMMARY OF THE INVENTION

In a first aspect, there is provided a salt of a sulfonated dyecomprising at least one ammonium cation, wherein the or each ammoniumcation comprises at least 3 hydroxyl groups. The ammonium cation is, ofcourse, the counterion for the anionic sulfonate moiety in the salt.

Optionally, the ammonium cation comprises at least 4 hydroxyl groups.

Optionally, the ammonium cation comprises at least 5 hydroxyl groups.

Optionally, the ammonium cation is of formula (A):

wherein:

-   R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are each independently selected from the    group comprising: H and —CH₂OH.

Optionally, the ammonium cation is selected from the group comprising:protonated triethanolamine; and protonated2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol.

Optionally, the dye is a sulfonated phthalocyanine dye.

Optionally, the dye is an IR-absorbing dye.

Optionally, the salt is of formula (I):

wherein:

-   Q¹, Q², Q³ and Q⁴ are the same or different and are independently    selected from a C₃₋₂₀ arylene group or a C₃₋₂₀ heteroarylene group;-   M is (H₂) or a metal selected from the group comprising: Si(A¹)(A²),    Ge(A¹)(A²), Ga(A¹), Mg, Al(A¹), TiO, Ti(A¹)(A²), ZrO, Zr(A¹)(A²),    VO, V(A¹)(A²), Mn, Mn(A¹), Fe, Fe(A¹), Co, Ni, Cu, Zn, Sn,    Sn(A¹)(A²), Pb, Pb(A¹)(A²), Pd and Pt;-   A¹ and A² are axial ligands, which may be the same or different, and    are selected from the group comprising: —OH, halogen, —OR³, —OC(O)R⁴    and —O(CH₂CH₂O)_(e)R^(e) wherein e is an integer from 2 to 10 and    R^(e) is H, C₁₋₈ alkyl or —C(O)C₁₋₈ alkyl;-   R³ is C₁₋₂₀ alkyl, C₅₋₁₂ aryl, C₅₋₂₀ arylalkyl or    Si(R^(x))(R^(y))(R^(z));-   R⁴ is C₁₋₂₀ alkyl, C₅₋₁₂ aryl or C₅₋₂₀ arylalkyl;-   R^(x), R^(y) and R^(z) are the same or different and are selected    from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl, C₁₋₁₂ alkoxy, C₅₋₁₂    aryloxy or C₅₋₁₂ arylalkoxy; and-   Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ are independently selected from the group    comprising: H and an ammonium cation comprising at least 3 hydroxyl    groups, wherein at least one of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ is said    ammonium cation.

Optionally, the salt is of formula (II):

wherein

-   M is (H₂) or a metal selected from the group comprising: Si(A¹)(A²),    Ge(A¹)(A²), Ga(A¹), Mg, Al(A¹), TiO, Ti(A¹)(A²), ZrO, Zr(A¹)(A²),    VO, V(A¹)(A²), Mn, Mn(A¹), Fe, Fe(A¹), Co, Ni, Cu, Zn, Sn,    Sn(A¹)(A²), Pb, Pb(A¹)(A²), Pd and Pt;-   A¹ is an axial ligand selected from —OH, halogen, —OR³, —OC(O)R⁴ or    —O(CH₂CH₂O)_(e)R^(e) wherein e is an integer from 2 to 10 and Re is    H, C₁₋₈ alkyl or C(O)C₁₋₈ alkyl;-   R³ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl or    Si(R^(x))(R^(y))(R^(z));-   R⁴ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl or C₅₋₁₂ arylalkyl;-   R^(x), R^(y) and R^(z) may be the same or different and are selected    from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl, C₁₋₁₂ alkoxy, C₅₋₁₂    aryloxy or C₅₋₁₂ arylalkoxy; and-   Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ are independently selected from the group    comprising: H and an ammonium cation comprising at least 3 hydroxyl    groups, wherein at least one of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ is said    ammonium cation.

Optionally, at least three of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ are saidammonium cation.

In a second aspect, there is provided an inkjet ink comprising a salt asdescribed above.

In a third aspect, there is provided a method of reducing kogation in aninkjet printhead, the method comprising: printing from the printheadusing an inkjet ink as described above.

Optionally, the printhead comprises a plurality of nozzles, each nozzlecomprising: a nozzle chamber containing said ink; a heater element forheating said ink; and a nozzle opening for ejection of ink.

Optionally, the heater element is comprised of titanium nitride or anitride of a titanium alloy.

Optionally, the heater element is comprised of titanium aluminiumnitride.

Optionally, the heater element is a cantilever beam suspended acrosssaid nozzle chamber.

Optionally, the printing includes at least 50 million drop actuations.

In a fourth aspect, there is provided an inkjet printhead comprising aplurality of nozzles, each nozzle comprising: a nozzle chambercontaining an inkjet ink as described above; a heater element forheating said ink; and a nozzle opening for ejection of ink.

Optionally, the heater element is comprised of titanium aluminiumnitride.

In a fifth aspect, there is provided a substrate having a salt asdescribed above disposed thereon or therein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partial perspective view of an array of nozzle assemblies ofa thermal inkjet printhead;

FIG. 2 is a side view of a nozzle assembly unit cell shown in FIG. 1;and

FIG. 3 is a perspective of the nozzle assembly shown in FIG. 2.

DETAILED DESCRIPTION Sulfonated Dye Salts

As used herein, the term “sulfonated dye” refers to any dye moleculebearing a sulfonate group. Sulfonated dyes are a well-known class ofcompound. Examples of some commercially available sulfonated dyes areFood Black 1 (Brilliant Black BN), Food Black 2 (Black 7984), Allura RedAC, Amaranth, Amido Black, Food Red 3 (Azorubine), Food Brown 3 (BrownHT), Chrysoine resorcinol (Resorcinol Yellow), Congo Red, Food Yellow 2(Fast Yellow), Hydroxynaphthol Blue, Lithol Rubine BK, Pigment Rubine,Orange B, Orange G, Orange GGN, Food Red 7, Acid Red 1 (Red 2G), FoodRed 2, Orange Yellow S, Sunset Yellow, tartrazine, Yellow 2G, Food Blue2, Food Green S, Food Green 2, Food Blue 5, and sulfonatedphthalocyanines (e.g. copper phthalocyanine, Aldrich Catalogue No.41,205-8). The Applicant has previously described sulfonatedphthalocyanine IR dyes, such as sulfonated naphthalocyanines (see U.S.Pat. Nos. 7,148,345 and 7,122,076).

As used herein, the term “phthalocyanine” refers to any compoundbelonging to the general class of macrocyclic phthalocyanines, andincludes naphthalocyanines, quinolinephthalocyanines etc, as well assubstituted derivatives thereof.

As used herein, the term “IR-absorbing dye” means a substance, whichabsorbs infrared radiation and which is therefore suitable for detectionby an infrared sensor. Preferably, the IR-absorbing dye absorbs in thenear infrared region, and preferably has a

_(max) in the range of 700 to 1000 nm, more preferably 750 to 900 nm,more preferably 780 to 850 nm. Dyes having a

_(max) in this range are particularly suitable for detection bysemiconductor lasers, such as a gallium aluminium arsenide diode laser.

Typically in the prior art, sulfonated dyes are provided in their saltform. The usual salts of sulfonated dyes are sodium salts, lithiumsalts, potassium salts and calcium salts. Such salts are inexpensive,readily soluble in aqueous-based media and easy to prepare. However,these salts suffer from severe kogation, particularly salts ofsulfonated phthalocyanines used in the Applicant's Memjet® printers.

By contrast, the ammonium salts according to the present invention,where the ammonium cation comprises at least 3 hydroxyl groups, exhibitreduced kogation compared to, for example, sodium salts.

Preferably, the ammonium cation comprises at least 5 hydroxyl groups. Anexample of such a cation is protonated “bis-tris” (protonated2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol), which exhibits vastlyreduced kogation compared to sodium salts. “Bis-tris”, which comprises 5hydroxyl groups, also exhibits reduced kogation compared to, forexample, triethanolamine which comprises 3 hydroxyl groups.

In the most general form of the present invention, the dye may be anysulfonated dye, such as those commonly used in printing inks. Theseinclude Food dyes, sulfonated phthalocyanines, sulfonated azo dyes andthe like.

The present invention has been shown to work particularly well withsulfonated phthalocyanines, which include sulfonated naphthalocyanines.Sulfonated phthalocyanine dyes may be metal-free or may comprise acentral metal atom moiety M. Optionally, M is selected from Si(A¹)(A²),Ge(A¹)(A²), Ga(A¹), Mg, Al(A¹), TiO, Ti(A¹)(A²), ZrO, Zr(A¹)(A²), VO,V(A¹)(A²), Mn, Mn(A¹), Fe, Fe(A¹), Co, Ni, Cu, Zn, Sn, Sn(A¹)(A²), Pb,Pb(A¹)(A²), Pd and Pt. Phthalocyanines having a range of central metalatom moieties are well known in the literature (see, for example,Aldrich Catalogue). Copper phthalocyanine tetrasulfonate is aparticularly well known example, used in cyan inkjet dyes. Sulfonationof phthalocyanines is readily achievable using standard sulfonationchemistry.

Optionally, M is selected from Si(A¹)(A²), Ge(A¹)(A²), Ga(A¹), Al(A¹),VO, Mn, Mn(A¹), Cu, Zn, Sn, and Sn(A¹)(A²). S

Optionally, M is Ga(A¹).

A¹ and A² are axial ligands, which may be the same or different.Optionally, A¹ and A² and are selected from —OH, halogen or —OR³.Optionally, A¹ and A² may be —OC(O)R⁴ or —O(CH₂CH₂O)_(e)R^(e) wherein eis an integer from 2 to 10 and R^(e) is H, C₁₋₈ alkyl or —C(O)C₁₋₈alkyl. Typically A¹ is a hydroxyl group (—OH).

R³ may be C₁₋₂₀ alkyl, C₅₋₁₂ aryl, C₅₋₂₀ arylalkyl orSi(R^(x))(R^(y))(R^(z)).

R⁴ may be C₁₋₂₀ alkyl, C₅₋₁₂ aryl or C₅₋₂₀ arylalkyl.

R^(x), R^(y) and R^(z) may be the same or different and are selectedfrom C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl, C₁₋₁₂ alkoxy, C₅₋₁₂aryloxy or C₅₋₁₂ arylalkoxy.

An example of a sulfonated phthalocyanine dye salt, which may be used inthe present invention is shown in formula (I):

wherein:

-   Q¹, Q², Q³ and Q⁴ are the same or different and are independently    selected from a C₃₋₂₀ arylene group or a C₃₋₂₀ heteroarylene group    (e.g. C₄ arylene to provide typical phthalocyanines or C₈ arylene to    provide naphthalocyanines);-   M is (H₂) or a metal selected from the group comprising: Si(A¹)(A²),    Ge(A¹)(A²), Ga(A¹), Mg, Al(A¹), TiO, Ti(A¹)(A²), ZrO, Zr(A¹)(A²),    VO, V(A¹)(A²), Mn, Mn(A¹), Fe, Fe(A¹), Co, Ni, Cu, Zn, Sn,    Sn(A¹)(A²), Pb, Pb(A¹)(A²), Pd and Pt;-   A¹ and A² are axial ligands, which may be the same or different, and    are selected from the group comprising: —OH, halogen, —OR³, —OC(O)R⁴    and —O(CH₂CH₂O)_(e)R^(e) wherein e is an integer from 2 to 10 and    R^(e) is H, C₁₋₈ alkyl or —C(O)C₁₋₈ alkyl;-   R³ is C₁₋₂₀ alkyl, C₅₋₁₂ aryl, C₅₋₂₀ arylalkyl or    Si(R^(x))(R^(y))(R^(z));-   R⁴ is C₁₋₂₀ alkyl, C₅₋₁₂ aryl or C₅₋₂₀ arylalkyl;-   R^(x), R^(y) and R^(z) are the same or different and are selected    from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl C₁₋₁₂ alkoxy, C₅₋₁₂    aryloxy or C₅₋₁₂ arylalkoxy; and-   Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ are independently selected from the group    comprising: H and an ammonium cation comprising at least 3 hydroxyl    groups, wherein at least one of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ is said    ammonium cation.

Usually, either three of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ or all of Z₁ ⁺, Z₂ ⁺,Z₃ ⁺ and Z₄ ⁺ are the ammonium cation, depending on the exact nature ofthe cation and the method of salt precipitation used in the preparation.

Optionally, Q¹, Q², Q³ and Q⁴ are the same and are each a C₄₋₁₀ arylenegroup (e.g. phthalocyanines and naphthalocyanines). Q¹, Q², Q³ and Q⁴may, of course, be substituted in accordance with the optional arylsubstituents described below.

The general synthesis of phthalocyanines in accordance with formula (I)are described in, for example, the Applicant's earlier U.S. Pat. Nos.7,148,345 and 7,122,076, the contents of which are herein incorporatedby reference. Specific salt syntheses are described hereinbelow.

Optionally, the groups represented as Q¹, Q², Q³ and Q⁴ are eachselected from an arylene group of formula (i) or (ii) below:

wherein:

-   R¹ and R² may be the same or different and are selected from    hydrogen, hydroxyl, C₁₋₁₂ alkyl, C₁₋₁₂ alkoxy, amino, C₁₋₁₂    alkylamino, di(C₁₋₁₂alkyl)amino, halogen, cyano, thiol, C₁₋₁₂    alkylthio, C₅₋₁₂ arylthio, nitro, carboxy, C₁₋₁₂ alkylcarbonyl,    C₁₋₁₂ alkoxycarbonyl, C₁₋₁₂ alkylcarbonyloxy or C₁₋₁₂    alkylcarbonylamino; and-   Z⁺═Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ or Z₄ ⁺.

A more specific example of a sulfonated dye salt, which may be used inthe present invention is the sulfonated naphthalocyanine salt shown informula (II):

wherein

-   M is (H₂) or a metal selected from the group comprising: Si(A¹)(A²),    Ge(A¹)(A²), Ga(A¹), Mg, Al(A¹), TiO, Ti(A¹)(A²), ZrO, Zr(A¹)(A²),    VO, V(A¹)(A²), Mn, Mn(A¹), Fe, Fe(A¹), Co, Ni, Cu, Zn Sn,    Sn(A¹)(A²), Pb, Pb(A¹)(A²), Pd and Pt;-   A¹ is an axial ligand selected from —OH, halogen, —OR³, —OC(O)R⁴ or    —O(CH₂CH₂O)_(e)R^(e) wherein e is an integer from 2 to 10 and Re is    H, C₁₋₈ alkyl or C(O)C₁₋₈ alkyl;-   R³ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl or    Si(R^(x))(R^(y))(R^(z));-   R⁴ is selected from C₁₋₁₂ alkyl, C₅₋₁₂ aryl or C₅₋₁₂ arylalkyl;-   R^(x), R^(y) and R^(z) may be the same or different and are selected    from C₁₋₁₂ alkyl, C₅₋₁₂ aryl, C₅₋₁₂ arylalkyl, C₁₋₁₂ alkoxy, C₅₋₁₂    aryloxy or C₅₋₁₂ arylalkoxy; and-   Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ are independently selected from the group    comprising: H and an ammonium cation comprising at least 3 hydroxyl    groups, wherein at least one of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺is said    ammonium cation.-   Typically, Z₁ ⁺═H; and Z₂ ⁺═Z₃ ⁺═Z₄ ⁺=the ammonium cation comprising    at least 3 hydroxyl groups.-   Alternatively, Z₁ ⁺═Z₂ ⁺═Z₃ ⁺═Z₄ ⁺=the ammonium cation comprising at    least 3 hydroxyl groups.-   Optionally, M is Ga(OH).

The term “aryl” is used herein to refer to an aromatic group, such asphenyl, naphthyl or triptycenyl. C₆₋₁₂ aryl, for example, refers to anaromatic group having from 6 to 12 carbon atoms, excluding anysubstituents. The term “arylene”, of course, refers to divalent groupscorresponding to the monovalent aryl groups described above. Anyreference to aryl implicitly includes arylene, where appropriate.

The term “heteroaryl” refers to an aryl group, where 1, 2, 3 or 4 carbonatoms are replaced by a heteroatom selected from N, O or S. Examples ofheteroaryl (or heteroaromatic) groups include pyridyl, benzimidazolyl,indazolyl, quinolinyl, isoquinolinyl, indolinyl, isoindolinyl, indolyl,isoindolyl, pyrrolyl, imidazolyl, oxazolyl, isoxazolyl, pyrazolyl,isoxazolonyl, piperazinyl, pyrimidinyl, pyridyl, pyrimidinyl,benzopyrimidinyl, benzotriazole, quinoxalinyl, pyridazyl etc. The term“heteroarylene”, of course, refers to divalent groups corresponding tothe monovalent heteroaryl groups described above. Any reference toheteroaryl implicitly includes heteroarylene, where appropriate.

Unless specifically stated otherwise, aryl and heteroaryl groups may beoptionally substituted with 1, 2, 3, 4 or 5 of the substituentsdescribed below. The optional substituent(s) are independently selectedfrom C₁₋₈ alkyl, C₁₋₈ alkoxy, —(OCH₂CH₂)_(d)OR^(d) (wherein d is aninteger from 2 to 5000 and R^(d) is H, C₁₋₈ alkyl or C(O)C₁₋₈alkyl),cyano, halogen, amino, hydroxyl, thiol, —SR^(v), —NR^(u)R^(v), nitro,phenyl, phenoxy, —CO₂R^(v), —C(O)R^(v), —OCOR^(v), —SO₂R^(v), —SO₂R^(v),—SO₂OR^(v), —NHC(O)R^(v), —CONr^(u)R^(v),—CONR^(u)R^(v),—SO₂NR^(u)R^(v), wherein R^(u) and R^(v) are independently selected fromhydrogen, C₁₋₁₂ alkyl, phenyl or phenyl-C₁₋₈ alkyl (e.g. benzyl). Where,for example, a group contains more than one substituent, differentsubstituents can have different R^(u) or R^(v) groups. For example, anaphthyl group may be substituted with three substituents: —SO₂NHPh,—CO₂Me group and —NH₂.

The term “alkyl” is used herein to refer to alkyl groups in bothstraight and branched forms. Unless stated otherwise, the alkyl groupmay be interrupted with 1, 2, 3 or 4 heteroatoms selected from O, NH orS. Unless stated otherwise, the alkyl group may also be interrupted with1, 2 or 3 double and/or triple bonds. However, the term “alkyl” usuallyrefers to alkyl groups having double or triple bond interruptions. Where“alkenyl” groups are specifically mentioned, this is not intended to beconstrued as a limitation on the definition of “alkyl” above.

Where reference is made to, for example, C₁₋₂₀ alkyl, it is meant thealkyl group may contain any number of carbon atoms between 1 and 20.Unless specifically stated otherwise, any reference to “alkyl” meansC₁₋₂₀ alkyl, preferably C₁₋₁₂ alkyl or C₁₋₆ alkyl.

The term “alkyl” also includes cycloalkyl groups. As used herein, theterm “cycloalkyl” includes cycloalkyl, polycycloalkyl, and cycloalkenylgroups, as well as combinations of these with linear alkyl groups, suchas cycloalkylalkyl groups. The cycloalkyl group may be interrupted with1, 2 or 3 heteroatoms selected from O, N or S and may be specificallyindicated as a heterocycloalkyl group. Examples of heterocycloalkylgroups are pyrrolidino, morpholino, piperidino etc. However, the term“cycloalkyl” usually refers to cycloalkyl groups having no heteroatominterruptions. Examples of cycloalkyl groups include cyclopentyl,cyclohexyl, cyclohexenyl, cyclohexylmethyl and adamantyl groups.

The term “arylalkyl” refers to groups such as benzyl, phenylethyl andnaphthylmethyl.

The term “halogen” or “halo” is used herein to refer to any of fluorine,chlorine, bromine and iodine. Usually, however, halogen refers tochlorine or fluorine substituents.

Any chiral compounds described herein have not been givenstereo-descriptors. However, when compounds may exist in stereoisomericforms, then all possible stereoisomers and mixtures thereof are included(e.g. enantiomers, diastereomers and all combinations including racemicmixtures etc.).

Likewise, when compounds may exist in a number of regioisomeric forms,then all possible regioisomers and mixtures thereof are included.

For the avoidance of doubt, the term “a” (or “an”), in phrases such as“comprising a”, means “at least one” and not “one and only one”. Wherethe term “at least one” is specifically used, this should not beconstrued as having a limitation on the definition of “a”.

Throughout the specification, the term “comprising”, or variations suchas “comprise” or “comprises”, should be construed as including a statedelement, integer or step, but not excluding any other element, integeror step.

Inks

The dye salts described above may be formulated in inkjet inks.Preferably, the inkjet ink is a water-based inkjet ink.

Water-based inkjet ink compositions are well known in the literatureand, in addition to water, may comprise additives, such as co-solvents,biocides, sequestering agents, humectants, viscosity modifiers,penetrants, wetting agents, surfactants etc.

Co-solvents are typically water-soluble organic solvents. Suitablewater-soluble organic solvents include C₁₋₄ alkyl alcohols, such asethanol, methanol, butanol, propanol, and 2-propanol; glycol ethers,such as ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, ethylene glycol monomethyl etheracetate, diethylene glycol monomethyl ether, diethylene glycol monoethylether, diethylene glycol mono-n-propyl ether, ethylene glycolmono-isopropyl ether, diethylene glycol mono-isopropyl ether, ethyleneglycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether,triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butylether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol mono-t-butyl ether, propylene glycol mono-n-propylether, propylene glycol mono-isopropyl ether, dipropylene glycolmonomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycolmono-n-propyl ether, dipropylene glycol mono-isopropyl ether, propyleneglycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether;formamide, acetamide, dimethyl sulfoxide, sorbitol, sorbitan, glycerolmonoacetate, glycerol diacetate, glycerol triacetate, and sulfolane; orcombinations thereof.

Other useful water-soluble organic solvents include polar solvents, suchas 2-pyrrolidone, N-methylpyrrolidone, -caprolactam, dimethyl sulfoxide,sulfolane, morpholine, N-ethylmorpholine, 1,3-dimethyl-2-imidazolidinoneand combinations thereof.

The inkjet ink may contain a high-boiling water-soluble organic solventwhich can serve as a wetting agent or humectant for imparting waterretentivity and wetting properties to the ink composition. Such ahigh-boiling water-soluble organic solvent includes one having a boilingpoint of 180° C. or higher. Examples of the water-soluble organicsolvent having a boiling point of 180° C. or higher are ethylene glycol,propylene glycol, diethylene glycol, pentamethylene glycol, trimethyleneglycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol,2-methyl-2,4-pentanediol, tripropylene glycol monomethyl ether,dipropylene glycol monoethyl glycol, dipropylene glycol monoethyl ether,dipropylene glycol monomethyl ether, dipropylene glycol, triethyleneglycol monomethyl ether, tetraethylene glycol, triethylene glycol,diethylene glycol monobutyl ether, diethylene glycol monoethyl ether,diethylene glycol monomethyl ether, tripropylene glycol, polyethyleneglycols having molecular weights of 2000 or lower, 1,3-propylene glycol,isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol,1,5-pentanediol, 1,6-hexanediol, glycerol, erythritol, pentaerythritoland combinations thereof.

The total water-soluble organic solvent content in the inkjet ink ispreferably about 5 to 50% by weight, more preferably 10 to 30% byweight, based on the total ink composition.

Other suitable wetting agents or humectants include saccharides(including monosaccharides, oligosaccharides and polysaccharides) andderivatives thereof (e.g. maltitol, sorbitol, xylitol, hyaluronic salts,aldonic acids, uronic acids etc.)

The inkjet ink may also contain a penetrant for accelerating penetrationof the aqueous ink into the recording medium. Suitable penetrantsinclude polyhydric alcohol alkyl ethers (glycol ethers) and/or1,2-alkyldiols. Examples of suitable polyhydric alcohol alkyl ethers areethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol monobutyl ether, ethylene glycol monomethyl etheracetate, diethylene glycol monomethyl ether, diethylene glycol monoethylether, ethylene glycol mono-n-propyl ether, ethylene glycolmono-isopropyl ether, diethylene glycol mono-isopropyl ether, ethyleneglycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether,triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butylether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol mono-t-butyl ether, propylene glycol mono-n-propylether, propylene glycol mono-isopropyl ether, dipropylene glycolmonomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycolmono-n-propyl ether, dipropylene glycol mono-isopropyl ether, propyleneglycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether.Examples of suitable 1,2-alkyldiols are 1,2-pentanediol and1,2-hexanediol. The penetrant may also be selected from straight-chainhydrocarbon diols, such as 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol.Glycerol or urea may also be used as penetrants.

The amount of penetrant is preferably in the range of 1 to 20% byweight, more preferably 1 to 10% by weight, based on the total inkcomposition.

The inkjet ink may also contain a surface active agent, especially ananionic surface active agent and/or a nonionic surface active agent.Useful anionic surface active agents include sulfonic acid types, suchas alkanesulfonic acid salts, -olefinsulfonic acid salts,alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acids,acylmethyltaurines, and dialkylsulfosuccinic acids; alkylsulfuric estersalts, sulfated oils, sulfated olefins, polyoxyethylene alkyl ethersulfuric ester salts; carboxylic acid types, e.g., fatty acid salts andalkylsarcosine salts; and phosphoric acid ester types, such asalkylphosphoric ester salts, polyoxyethylene alkyl ether phosphoricester salts, and glycerophosphoric ester salts. Specific examples of theanionic surface active agents are sodium dodecylbenzenesulfonate, sodiumlaurate, and a polyoxyethylene alkyl ether sulfate ammonium salt.

Suitable nonionic surface active agents include ethylene oxide adducttypes, such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenylethers, polyoxyethylene alkyl esters, and polyoxyethylene alkylamides;polyol ester types, such as glycerol alkyl esters, sorbitan alkylesters, and sugar alkyl esters; polyether types, such as polyhydricalcohol alkyl ethers; and alkanolamide types, such as alkanolamine fattyacid amides. Specific examples of nonionic surface active agents areethers such as polyoxyethylene nonylphenyl ether, polyoxyethyleneoctylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylenealkylallyl ether, polyoxyethylene oleyl ether, polyoxyethylene laurylether, and polyoxyalkylene alkyl ethers (e.g. polyoxyethylene alkylethers); and esters, such as polyoxyethylene oleate, polyoxyethyleneoleate ester, polyoxyethylene distearate, sorbitan laurate, sorbitanmonostearate, sorbitan mono-oleate, sorbitan sesquioleate,polyoxyethylene mono-oleate, and polyoxyethylene stearate. Acetyleneglycol surface active agents, such as2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol or3,5-dimethyl-1-hexyn-3-ol, may also be used.

The inkjet ink may also include a biocide, such as benzoic acid,dichlorophene, hexachlorophene, sorbic acid, hydroxybenzoic esters,sodium dehydroacetate, 1,2-benthiazolin-3-one, 3,4-isothiazolin-3-one or4,4-dimethyloxazolidine.

The inkjet ink may also contain a sequestering agent, such asethylenediaminetetraacetic acid (EDTA).

The inkjet ink may also contain a singlet oxygen quencher. The presenceof singlet oxygen quencher(s) in the ink reduces the propensity for theIR-absorbing dye to degrade. The quencher consumes any singlet oxygengenerated in the vicinity of the dye molecules and, hence, minimizestheir degradation. An excess of singlet oxygen quencher is advantageousfor minimizing degradation of the dye and retaining its IR-absorbingproperties over time. Preferably, the singlet oxygen quencher isselected from ascorbic acid, 1,4-diazabicyclo-[2.2.2]octane (DABCO),azides (e.g. sodium azide), histidine or tryptophan.

Substrates

As mentioned above, the dyes of the present invention are especiallysuitable for use in Hyperlabel™ and Netpage systems. Such systems aredescribed in more detail below and in the patent applications listedabove, all of which are incorporated herein by reference in theirentirety.

In the case of Hyperlabel™ and Netpage application, the IR dye isdisposed on a substrate in the form of a coding pattern readable by anoptically imaging sensing device. An example of a suitable codingpattern is described in U.S. Pat. No. 6,832,717, the contents of whichis herein incorporated by reference. Typically, the coding pattern isdisposed over a substantial portion of an interface surface of thesubstrate (e.g. greater than 20%, greater than 50% or greater than 90%of the surface).

Preferably, the substrate is IR reflective so that the dye disposedthereon may be read by a sensing device. The substrate may be comprisedof any suitable material such as plastics (e.g. polyolefins, polyesters,polyamides etc.), paper, metal or combinations thereof. The substratemay be laminated.

For netpage applications, the substrate is preferably a paper sheet. ForHyperlabel™ applications, the substrate is preferably a tag, a label, apackaging material or a surface of a product item. Typically, tags andlabels are comprised of plastics, paper or combinations thereof.

Thermal Bubble-Forming Inkjet Printhead

As mentioned above, the dyes of the present invention are especiallysuitable for use in the Applicant's thermal inkjet (“Memjet®”)printheads. A brief description of a thermal inkjet printhead nowfollows. Further details of such printheads may be found in thecross-referenced patents and patent applications listed above, which areincorporated herein by reference.

Referring to FIG. 1, there is shown a part of printhead comprising aplurality of nozzle assemblies. FIGS. 2 and 3 show one of these nozzleassemblies in side-section and cutaway perspective views.

Each nozzle assembly comprises a nozzle chamber 24 formed by MEMSfabrication techniques on a silicon wafer substrate 2. The nozzlechamber 24 is defined by a roof 21 and sidewalls 22 which extend fromthe roof 21 to the silicon substrate 2. As shown in FIG. 1, each roof isdefined by part of a nozzle plate 56, which spans across an ejectionface of the printhead. The nozzle plate 56 and sidewalls 22 are formedof the same material, which is deposited by PECVD over a sacrificialscaffold of photoresist during MEMS fabrication. Typically, the nozzleplate 56 and sidewalls 21 are formed of a ceramic material, such assilicon dioxide or silicon nitride. These hard materials have excellentproperties for printhead robustness, and their inherently hydrophilicnature is advantageous for supplying ink to the nozzle chambers 24 bycapillary action.

Returning to the details of the nozzle chamber 24, it will be seen thata nozzle opening 26 is defined in a roof of each nozzle chamber 24. Eachnozzle opening 26 is generally elliptical and has an associated nozzlerim 25. The nozzle rim 25 assists with drop directionality duringprinting as well as reducing, at least to some extent, ink flooding fromthe nozzle opening 26. The actuator for ejecting ink from the nozzlechamber 24 is a heater element 29 positioned beneath the nozzle opening26 and suspended across a pit 8.

Typically, the heater element 29 is comprised of a titanium nitride or anitride of a titanium alloy. An example of titanium alloy nitride istitanium aluminium nitride. However, it will be appreciated that othermaterials may be used as the heater element 29, and the presentinvention is not restricted to those materials specifically recitedherein.

Current is supplied to the heater element 29 via electrodes 9 connectedto drive circuitry in underlying CMOS layers of the substrate 2. When acurrent is passed through the heater element 29, it rapidly superheatssurrounding ink to form a gas bubble, which forces ink through thenozzle opening. By suspending the heater element 29, it is completelyimmersed in ink when the nozzle chamber 24 is primed. This improvesprinthead efficiency, because less heat dissipates into the underlyingsubstrate 2 and more input energy is used to generate a bubble.

The heater element 29 shows less kogation using inks in accordance withthe present invention, when compared with inks comprising, for example,sodium salts of sulfonated dyes. Less kogation is observed after about20 million drop ejections, about 30 million drop ejections, about 40million drop ejections or about 50 million drop ejections.

Consequently, the lifetime of the printhead is increased by at least2-fold, at least 3-fold, at least 4-fold or at least 5-fold whencompared with inks comprising sodium salts of sulfonated dyes.

As seen most clearly in FIG. 1, the nozzles are arranged in rows and anink supply channel 27, extending longitudinally along the row, suppliesink to each nozzle in the row. The ink supply channel 27 delivers ink toan ink inlet passage 15 for each nozzle, which supplies ink from theside of the nozzle opening 26 via an ink conduit 23 in the nozzlechamber 24.

A MEMS fabrication process for manufacturing such printheads wasdescribed in detail in U.S. application Ser. No. 11/246,684 filed onOct. 11, 2005, the contents of which is herein incorporated byreference.

The invention will now be described with reference to the followingexamples. However, it will of course be appreciated that this inventionmay be embodied in many other forms without departing from the scope ofthe invention, as defined in the accompanying claims.

EXAMPLES

In our earlier U.S. Pat. No. 7,148,345 and U.S. Patent Application No.60/851,754 (Attorney Docket No. IRB022US, filed on Oct. 16, 2006), thecontents of which are herein incorporated by reference, we described thepreparation of various salts of gallium naphthalocyanine tetrasulfonicacid 1. The skilled person will readily appreciate that salts accordingto the present invention may be readily prepared from correspondingsulfonic acids by conventional methods.

In testing a range of alternative salts, including those of the alkalimetals it was unexpectedly found that when the salt of acid 1 comprisesprotonated “bis-tris” [2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol]2 as the counterion, kogation on TiAlN heaters is greatly reduced andthe effective lifetime of a thermal inkjet printhead is increased by atleast 3-5-fold.

A further advantage of the protonated bis-tris counterion is that itgreatly facilitates the preparation and isolation of the correspondingsalt of the acid 1. In general, salts of acid 1 are convenientlyprepared by mixing an amine or metal hydroxide with the acid inmethanol/water (ca. 80:20), diluting with a fixed amount of ethylacetate and filtering the product. Most of the salts, especially thealkali metal salts, precipitate as fine solids that are slow to filter,clogging membranes easily. However, in the case of bis-tris salts, thesehave a lower solubility in the reaction medium and flocculate readily toafford a much coarser precipitate that filters easily. This lowersolubility causes the product to precipitate and stop at thetris(bis-tris) inner salt (3) stage rather than proceed on to thetetrakis(bis-tris) salt (4) form.

Example 1 Preparation of the Bis-Tris Salt (3)

Bis-tris 2 (26.3 g; 0.125 mol, 7 equiv.) was dissolved completely inmethanol (150 mL) and water (40 mL) and then gallium naphthalocyaninetetrasulfonic acid 1 (20.1 g; 0.018 mol) was added with stirring to givea green suspension. The reaction mixture was allowed to stir for 20 hand then ethyl acetate (350 mL) was added. After stirring for another 10min. the reaction mixture was poured into ethyl acetate (250 mL) in a 2L conical flask with vigorous stirring. The precipitated salt wasfiltered off on a sintered glass funnel under gravity, the filtratedraining readily at a fast rate. The moist solid was then washed withmethanol (4×50 mL) under gravity and then the last traces were removedby suction. The resulting solid was air-dried before being dried underhigh vacuum at 65° C. The bis-tris salt was obtained as a green powder(23.7 g; 76%).

Example 2 Formulation of IR Inks

Dye salts 5 and 6 were prepared similarly to salt 3 prepared in Example1.

Each IR dye salt (3, 5, 6) was formulated according to the componentslisted in Table 1 and filtered through a 0.2 μm PTFE filter membrane.

TABLE 1 Composition of an ink vehicle used for making up IR inkscontaining IR dye at 4 mM Ink component % w/w ethylene glycol 5-151-propanol 5-15 2-pyrrolidinone 5-15 biocide 0.2 water balance

Example 3 Kogation Testing

Each IR ink containing the respective dye salt (3, 5 or 6) was printedusing the thermal inkjet printhead described in connection with FIGS.1-3. The heater elements 29 were observed under high magnification after50 million actuations.

The ink containing the sodium salt 6 performed the worst and a highdegree of kogation was observed after 50 million actuations. The inkcontaining the triethanolamine salt 5 performed better than the sodiumsalt 6, although a moderate amount of kogation was still observed after50 million actuations. However, the ink containing the “bis-tris” salt 3performed excellently with minimal or no kogation observed after 50million actuations.

It will be appreciated by ordinary workers in this field that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

1. A sulfonated dye salt of formula (II):

wherein M is Ga(A¹); A¹ is an axial ligand selected from the groupconsisting of: —OH and halogen; and Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ areindependently selected from the group consisting of: H and an ammoniumcation comprising at least 3 hydroxyl groups, wherein at least one of Z₁⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ is said ammonium cation.
 2. The salt of claim 1,wherein said ammonium cation comprises at least 4 hydroxyl groups. 3.The salt of claim 1, wherein said ammonium cation comprises at least 5hydroxyl groups.
 4. The salt of claim 1, wherein said ammonium cation isof formula (A):

wherein: R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ are each independently selected fromthe group consisting of: H and —CH₂OH.
 5. The salt of claim 1, whereinsaid ammonium cation is protonated2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol.
 6. The salt of claim1, wherein at least three of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄ ⁺ are said ammoniumcation.
 7. The salt of claim 1, wherein each of Z₁ ⁺, Z₂ ⁺, Z₃ ⁺ and Z₄⁺ is said ammonium cation.
 8. An inkjet ink comprising a salt accordingto claim
 1. 9. A method of reducing kogation in an inkjet printhead,said method comprising: printing from the printhead utilizing an inkjetink according to claim
 8. 10. The method of claim 9, wherein saidprinthead comprises a plurality of nozzles, each nozzle comprising: anozzle chamber containing said ink; a heater element for heating saidink; and a nozzle opening for ejection of ink.
 11. The method of claim10, wherein said heater element is comprised of titanium nitride or anitride of a titanium alloy.
 12. The method of claim 11, wherein saidheater element is comprised of titanium aluminium nitride.
 13. Themethod of claim 10, wherein said heater element is a cantilever beamsuspended across said nozzle chamber.
 14. The method of claim 9, whereinsaid printing includes at least 50 million drop actuations.
 15. Aninkjet printhead comprising a plurality of nozzles, each nozzlecomprising: a nozzle chamber containing an inkjet ink according to claim9; a heater element for heating said ink; and a nozzle opening forejection of ink.
 16. The inkjet printhead of claim 15, wherein saidheater element is comprised of titanium aluminium nitride.
 17. Asubstrate having a salt according to claim 1 disposed thereon ortherein.